Dynamo-electric machine



Malyv 15, 1923. 1,454,925

R. E. HELLMUND v DYNAMO v ELECTRIC MACHINE Filed Nov. 19, 1917 6 SheetS-Shee l '--1 l l l l l wlTNEssEs; A Y iNvENToR l .MS/Ema Y Rada/f E. Hel/muffa' l I BY 2 ATTORNEY May 15, 1923.

DYNAMO ELECTRIC MACHI NE Filed Nov. 19 1917 6 Sheets-Sheet 2 I H73 Arma/arE/F/Ux Fiy. F/7. /0

/J /e 577 /J We ffl-28 WITNESSES': Y INVENTCR 1,454,925 y R. E. HELLMUND May 15, 1923. 1,454,925

. l R. E. HELLMUND DYNAMO ELECTRIC MACHINE Filed Nov. 19, 1917 Y ssheets-sheet 6mund May 15, 1923. i 1,454,925 R. E. HELLMUND DYNAMO ELECTR I C MACHI NE Filed Nov. 19, 1917 s sheets-Sheet 4 We@ @wy/HY V ATTORNEY May 15, 1923. 1,454,925 R. E. HELLMUND I DYNAMO ELECTRIC MACHINE 1 Filed Nov. 19', 1917 e sheet's-sheet e WITNESSES:

- ATroRNEY Patented May l5, ltl,

unirse PENNSYLVANA, ASSIGNOR T0 WESTING- HOUSE ELECTRC & lVIANUIEACURNG COMPANY, .A CORPORATION OF PENNSYL- VANIA.

Application filed November To /LZ 'to/tom if; may concern lie it known that l, l?. einem# lll. linnn- MUND. a citizen oi" the German lilmpire, ainl a resident ot Swissvale. in the county ot .flllegheny and ate o'l' Pennsylvania, have invented a new and usetul lmprovenient in Dynaino-Electric lwlzichincs, ot which the tollowing is a specitication.

My invention relates to machines and especially to alternati" surrent commutatm motors oit the singleqiliase type that employ sliort-circuited :.iumiturc brushes tor the purpose et furnishing or intiuencing the exciting eldtlux.

lt is well known lin the art, that motors ot the above-indicated character, which correspend to what may be termed armatureexcited motors,77 are incapable ot' priulucing` sufficient starting torque to accelerate the motors and, in many cases, will not rot-.ite at all unless some externai device.. such :is an inductive coil, is connected across certain ot the armature brushes to cause a reduction ot the demagnetizing `currents iiowing in the armature, under start-ing conditions, whereupon the torque relations are suitable tor etliecting motor rotation.

lt is the object ot my present invention to provide a. motor ot the above-indicated general class which shall be selig-starting with out necessitating the use ot" special starting connections, external inductive devices or any other auxiliary apparatus giving, at the same time, satisfactory commutation.

More specifically stated, it one 'object o'lj my invention to so locate the stator exi citing or torque-producing lield winding with respect to the pairs ot short-circuited armature brushes influencing the excitation that the resultant ott-he stator-exciting 'flux and the armature-demagnetizing flux will be o'li su'mcient amplitude to insure suitable starting and accelerating operation ot the motor.

Other objects of my invention will become evident from the following detailed description and are forth with particularity in the appended claims.

My invention may best be understood by reference to the accompanying drawings, wherein Fig. l is a fragmentary view in diagramn'iatic end elevation, ot a dynamo-electric machine constructed in accordance with the present inrention; Fig. .5 is a combined dynamo-clectric TREC ITACHNE.

19, 1917. Serial NO. 202,899.

diagrammatic view serving to illust-rate the relations of fluxes in the machine and also serving to further depict the relation ot stator and armature windings; Fig. 3 and Fig. e are flux charts, corresponding to Fig. 2, and illustrating the flux conditions in the machine in various stages ot operation; Fig. 5 a similar chart, showing the ilu); relations in slightly mediiied construction; i `ig. t3 'to i8, inclusive, are simpliied diagrammatic views ot various modilied connections of the complete armature and stator windings that may advantageously be einployed in conjunction with my invention, Fig. 19 and Fig. 2O are views, respectively corresponding to Fig. l and Fig. 2, ot a modified torni of the invention; Fig. 2l is a l'lux chart serving to further illustrate the Alinx relations in the machine of Fig. 19, under a different ope 'ating condition; Fig. 22 is a view, corresponding to Fig. 2, of another nunliication et my invention; and Fig. Q3 to Fig. 3l., inclusive, are diagrammatic views of further modications ot' winding interconnections embodying the invention.

Referring to Fig. l of the drawings, the structure shown comprises a rotatable armature A, oi the familiar commutator type. having a plurality ot pairs ofishort-circuited brushes l and 3 and 2 and il, respectively; and a stator or field-magnet structure Sl, preferably of the customary laminated type.l that concentrieally encloses the armature A..

The brushes, short-circuited i'or exciting purposes, are symmetrically disposed upon the ari'nature comnnitator, the brushes comprising each individual pair being spaced in acwordance with proper design considerations. pre'lierably by an angle of approximately 72o, as hereinafter more fully set forth. rnnproximately opposite the brushes l. 2, El and il are located a plurality ot relatively large stator slots 5, 6, 5 and 6, respectivelyH while a plurality of smaller slots 9 and 9 are located between the large slots i3 and 5, and also between the other large slotso and (5', and a 'further set ot regularlyrecurring slots il and il extend outwardly irom each et the large slots 5 and 5 to the correspoin'ling slots 5 and G.

.Si main or exciting fieldnvinding coil 8 is wound in the large slots 5 and (l, as shown in the lower portion ot Fig. 2, while a similaily-constructed, but oppositely-wound,

coil 7 is located in the slots 5 and G. ln-

ducing-iield-winding coils 13 and 14, wound in the various slots 9, 9, ll and ll, in accordance with the familiar concentric type of.' winding, are also provided. In this way, an exciting or working flux, indicated by the dotted lines and the corresponding legend in Fig. 2 is induced by the exciting windings 7 and 8 on the stator. The axis of this flux is marked \,A2 in Fig. l. rl`he windings 13 and 14, located in the slots 9, 9', ll, ll, etc., induce the so-called inducing field flux along an axis lili, in Fig. 1. The latter flux serves the wolhknown purpose of transferring a voltage proportional io that ot the iinlucing field winding by transformer action into the armature working conductors or inductors. These working .inductors, carrying the working eurreiit, which, together with the main flux having the axis Ali/X2, produces torque, are located in Fig. l between the pairs ofbrushes l and 2, and 3 and 4-, and are marked WW.

During starting conditions, the main flux set up by the exciting field winding induces, by transformer action, a. voltage in the soealled armature magnetiZing-circuit conductors or inductors marked e c in Fig. l and located between the pairs of brushes l and 3 and 2 and l. Since the arn'iature-ex4 citing-circuit, of which these conductors form a part, is close-circuited by virtue of the external connections between the brushes l and 3, and 2 and el, respectively, a currentis set up in the armature-magnetizing or exciting inductors. These inductors act, therefore, like the secondary turns of a transformer, that isj they have a demagnetizing effect upon the main flux. This effect may be represented by a flux having the form of the solid stepped line in Fig.

designated as Armature Flux.

vAs is well-known` these two fluxes, at starting, substantially annul each other in machines ot' the prior art and, consequently, an insufficient torque to rotate the armature is produced. However, by concentrating` the main or exciting-field-winding coil-sides in the illustrated large stator slots approximately opposite the armature brushes, the resultant flux. that is produced by the exciting stator flux and the armature demagnetizing flux, is suflicient to produce a suitable starting torque, as indicated by the rectangular cross-hatched portion of the flux cha-rt in Fig. 2. The stepped cross-hatched areas do not aid in the development of torque, since their resultant effect upon the excitingcircuit conductors, which are spanned by the pairs of short-circuited brushes, is substantially equal to zero.

The reason for obtaining a suitable starting torque in machines constructed according to the present invention, without requiring a special starting connection or the use of an external inductive device, may be explained as follows. A certain material portion of the lines ot' force set up by the armature exciting or magnetizing currents does not interlink with the exciting field windings 7 and 8 by reason of the location thereof, or, in other words, a relatively large degree of leakage of the armature'magnetizing` fiux takes place in the zones that are spanned by the shortcircuited brushes. Consequently, the resultant self-induction in the arn'iature magnetizing-circuit produces an equilibrium of' voltage when the active armature demagnetizing flux caused by the armature currents, the value of which is dependent upon the active armature exciting flux. is .smaller than the exciting stator flux, or. in other words. a resultant torque-producing flux passes through the armature.

As the motor increases in speed, the voltage that is produced by rotation ol the armature indueing circuit inductors, through the familiar induced or cross-field flux, serves to diminish the demagnetizing currents in the armature, and the arrangement of parts may readily be made such that this demaofnetizing current will be substantially nullifiped under normal load conditions, or have an effect assisting that of the stator eX- citing winding.

If it is assumed, in accordance with the design of prior-art machines, that the resistance and leakage reactance of the armature magnetizing turns e between the shortcircuited brushes is negligible, it evident that the resultant voltage that is induced in such turns must be equal to zero when the motor is about to start. .3y mathematically proceeding from this assumption, the relative proportions of the fluxes that are shown in Fig. 2 may be calculated, and the various parts of the motor may be so designed as to produce a desirable value of' starting torque fiux, as represented by the cross-hatched area above the horizontal datum line. For example, the distance between brushes such as l and 2, corresponds to the distance between the large stator slots and (3 and to the width ofthe dotted rectangle representing exciting stator'flux. By computing the results of varying the distance in question over a. relatively wide range, it is found that the resultant or available excitingY field fiux during the starting operation varies with the distance between the unconnected brushes, such as l and 2. In this way, it may be determined that the distance between the short-circuited brushes 1 and 3 should equal about 4 of the entire polar circumference to obtain a maximum value for the resultant flux rectangle above the horizontal datum line of Fig. 2. However, when the machine is running, the exciting field flux will be more effective, with a considerably larger distance between the llU brushes l and Q, and, since it has been caleulated that the starting torque decreases rather slowly in proportion to the increase of this distance, it appears that a value corresponding to approximately (50% of the polar circumference represents the best cornpromise condition for both starting and running operation. Consequently, the span covered by each pair or short-circuited brushes preferably equals about 20% ot the circumference, or 72 electrical degrees.

As previously mentioned, a voltage is induced in the armature inductors between the short-circuited brushes l and 3 and 2 and l upon rotation oli the armature in the customarily provid inducing field flux, and this voltage tends to decrease the demagnetizing.

action in the armature until a substantially Zero value thereof is attained under certain speed and load conditions. Asthe motor accelerates, the stator current also inherently decreases. Fig. 3 represents fluit conditions in the machine when the stator current is approximately equal to one-halt ot the starting' current, with the armature demagnetizing current substantially zero, and., in this case, a relatively large available torque, represented by the cross-hatched rectangles, .is provided.

Upon still further acceleration ot the motor, the magnetizing currents in the armature flow in the opposite directionr and assist the stator lield flux in order to inherently maintain conditions of equilibrium, whereupon conditions similar to that shown in Fig. l are secured, the stator current in the case corresponding` to Fig. 4t being assumed to be about one-balic of the current corresponding to the condition that is illustrated in Fig. 3. The voltages induced by the exciting field flux in the armature magnetizing turns are, practically speaking, approximately th same in both cases, which means that the speed of the motor in the two conditions varies but slightly, assuming, oi course, that the inducing field flux has not materially changed. Consequently, it ilollows that a load change oit considerable value does not very seriously affect the speed et a motor constructed in accordance with the present invention, or, in other words, a motor of practically constant-speed characteristic is provided.

Instead of locating the exciting field winding coils 7 and S exactly in alinement with the several armature brushes, the winding under conside-rationv may be arranged to span a somewhat different are in order to permit a more favorable 'flux distribution for the inducing field winding and to bring about better ceinmutatine` conditions One suchstructure is indicated in Fig. 5, wherein it, will be seen that` the width oi the dotted rectangle representing` 'exciting stator flux, which width corresponds to the distance between the large stator slots 5 and (i, is somewhat less than the distance between the uuconnected brushes l and 2. Under s ch conditions, some ot' the armature working-circuit induetors lll, lll/l between pairs ot shortcircuited brushes are under the influence ot negative or reversed field fluxes, which, ot course, tends to reducl the resultant or torque-producing linx, as clearly indicate l by the several cross-hatched portions oit ll'ig. 5, lt will be observed that the available torque increases as the distance between the stator slots in question approaches the distance between the brushes l and However, a slight difference is not prohibitive trom a practical standpoint and is, therelore, permissible in the event oil producing other advantages, such as better commu?,ny tion or less expensive construction. By mathematical calculations, similarly to those previously mentioned, the best compromise value lor the distance between the large stator slots, which corresponds to the width ot the dotted rectangle in Fig. may be determined. Y

The previous structural Yfeatures may be employed to advantage in connection with a variety ot armature and field-windine` cennections, some ot which are illustrated in Fig. G to Fig. lo, inclusive. ln Fifi'. 6. the excitingor tmque-procucii1g field-winding coils 7 and 8 are shown located in the axis that passes mirway between the brushes l. and 2, while the inducing` lield-windinncoils 13 and lll are located inquadrature relation to the exciting field winding'. The illustrated supply-circuit terminals l5 and l may be connected to any customary souri' of energy, such the secondary '-riinlina` o a transformer, as shown in Fiy A ample. The circuits shown in i 6 involve the series connection et' the inducing' fieldwinding` and the exciting [ield-udndinny across the supply terminalswith the pairs ot short-circuited armature brushes acting as single terminals and connected to Ythe supply terminal l5 and to a point intermediate the two field windings, respectively.

ln Fig. 'i'. the excitingHeld-whirling lcoils 7 and 8 are separated and are connecftzul in parallel relation across the short-circuited pairs ot brushes, while the inducing-fieldwindinn coils 13 and 14 are connected directly to the supply circuit.

ln this case., the exciting field winding is magneti ed by the armature working cui"H rent and is. therefore, in erect phase rel tion with that current. Assuming that the armature inagnetizing current is practicallv zero under normal operating; conditions. it is eif'ident that no corrective `Voltage in the armature magnetizinaY circuit is reuuired to compensate tor the ohinic resistance ot that circuit. or to improve commutating conditions.'

Iii

Fig. S again shows the direct connection oi the indue ng winding to the supply-cn'- ninals, and, in addition, the armais connected in series relation with the excltnig-tield-winding coils i and S in parallel relation to the inducing' held-wind* ing, that is, directliv across the snpplj,7 cireu'o ln this c se, also, the phase relations set ltorth in connection with Fie. 7 obtain.

ln Fig, 9. the two field windings are connected i series relation to the siigplg,v conductors, and the armature A. is connected in parallel relation to the excitingield win din Fig. 10 illustrates the combination 'ot the two heli/l windinf` An a single symmetricallj,7 distributed stator winci` n; 2t), the eiiecti'ife .j axis oli which is inclined at a ined angle in accordance with the predeter;

relati proportion ot parts, as will be nnle ood.

11. the short-circuited brushes 1 been replaced by a single brush which is located .midway between the ositions of the brushes 1 and that are eniplojif'ed in the i'n'ci'ieus ligures, and the ids-tern ot connections :a otherwise similar to that shown in Fig, S.

l? i i rs. troni Fg.

snbstitinion o1( a single brush Q1 Afor the s 1i. and -l, the brush 21 being n-.ediate tite locations ot the brushes 1 and 3, as in and 3 have oi 0 (S onl)7 in the placed nu,

shortcircuited Fig. 11.

ln Fig. 13, the inducing field windingl and the exciting' iield winding are connected ben tween theisupply-circuit terminals and 16, while the armature A oi' the A/l-brush type i iected in parallel relation to the e eid-winding coils 'T and 8, but in the l relation to that shown in Fie'. 9.

141, a secondary transformer windshown as connected lietween the -circnit terminals 15 and 1G., a switch "ring to .fonnect the terminal le to the 'i'ia' lich ,-iinding, while a second su Vitch 'res to connect the lield winding to en mermediatc point in the secondariY tr; isn T22. Thus. it i'lesired. the andv the armature g. isequently. upon the cliisure olf switch 2rand the opening ot switch Q2, the Afamiliar doubly-ted or i transtormcnwindiiction i i nnection oiitains, the two field windings being connectedL acie s the inninr portion of the transformer winding, while the arinature A and the exciting field-winding are connected across a intermediate port-ion thereof.

ln Fig, 16, the secondan,Y transformer winding T) is shown as associated with the cnstemarv primar).y transformer winding T1. which eonncctiul through the cxi'fiting tield-windingV coils T and S to suitable supply-circuit confhictors that are respectively marked Trolleyv and Ground. ln this case, the arlnatn re nd the .inducing-fieldwinding coils 13 and 14e are connected to the secondary transformer wiiiding 2 in accordance with the well-lmown tranyforieer conduction circuits.

ln some cases, it may be desirable to slightl)7 adjust the phase of the voltage in the armature magnctizing circuit in order to compensate lor the olnnic resistance thereot or to improve commutating com'litions. Fig. 17 discloses a system wherein the desired result is obtained by connecting a small portion ol the inducing field winding in the armature magneti/:ing circuit. The illustrated shortcircuited-brush arrangement adapts the motor tor satiedactory operation at syl'ichrenous speed, in accordance with Jfamiliar principles.

In Fig. 1S, a sin Vilar phase-adjusting effect is accomplished by connectinga transformer Q1 in certain ot the machine circuits. The transformer 211 compri-es a magnetizable core member and a plrn'alit)v ot coils 2, 27 and 2S surrounding the core and respectively connected across the brushes 1 and 3, across the brushes 2 and 4;, and across the supply-circuit terminals 15 and 1G. A plurality of movable taps 260, and 27a are also provided for connectinfr the respective supply-circuit terminals 1o and 16 directly to the transformer coils 2G and 27, which are thus energized both inductively .from the transformer winding 28 and conductively through the taps 26a and 27a. The phase et the exciting currents that are induced in the armature A may be modilied in either ot the ways shown in Fig. 17 and Fig. 1S to eliect the desired compensation KLfor the resistance of' the armature magnetiaing` circuit or to improve the comniutating; characteristics of the machine.

Fig. 19 shows a modified structure wherein theJ armature A having` the pairs'ot' shortcircuiting brushes. 1 and El, and 2 and Ll, respectively, `is enclosed by a stator 'S2 that is provided with al plurality ot relatively large slots 30 and 31 that are located along the line that bisects the angle between each pair oit lshort-circuited exciting brushes, the stator vcore member beingl also provided with a plurality of sets of smaller slots 32, within which are located a plurality ot distributed lield coils and Si or producing the desired inducing-lield-winding this, under operating conditions. The large slots 30 and '31 are provided with exciting-fieldwindingrcoi'ls 87 and 38, 'the relative location of the short-circuited brushes and the large slots being-'such thatthe ma gne'tic leakage between the exciting-ield-winding turns and 'the armature-circuit-magnetizing turns is relatively large. as previously described in connection with Fig. 1.

The relation ot field windings is also shown in Fig. 2O in conjunction with a ihn-1 chart that graphically illustrates the exciting` "stator linx, the armature demagnetizinp; tlux and y'the resultant flux, in the manner hereinbefore explained.

The resultant or torque-producingl flux obtained by the structure linst described is rather small, and, consequently, would not be 'suitable tor starting machines of large capacity orstartingl friction, etc.

Furthermore. the 'cross-hatched rectangle7 which represents the available torque-producinp; flux in the present instance, is located below the zero or datum line, and, consequently, the motor will rotate in the opposite direction from that set 'tort-h in connection with Fig. 1 and Fig'. 2, provided, oli course, that. otherwise. the conditions are equal. As the motor accelerates. the crossliel(3l-winding` coils 33 and 34 induce a voltage between the short-circuited brushes ot eachset,`which voltage is also opposite to the rotational voltage induced in the previously-described typev oi motor. Consequently. the induced voltage in the present case will tend to increase the armaturemagn'etizing currents, while the stator current decreases. ais before, upon an increase of motor speed.` Fig'. '21 shows the ilus conditions in various parts ot the machine when the motor rhas Iaccelerated to a certain point. i Since the resultant ield Hui; induces a voltage in the stator-exciting' field winding' that is opposite to 4the actual linx :produced byv that field winding-,Uit liis evident, from a consideration of "vectorial flux relations, that a leading' voltage is thus induced in the exciting-held winding, whereby a predetermined degree of power-factor compensation is eiliected.

A; desirable increase ot such resultant flux may be obtained bythe use et the windim;` arrangement that is shown in the lower part ot Fig. 22, which combines the structures ot' l and oi' Fig. 2O to a certain eX- tent. ln general, one small-span coil 4S of the exciting-held winding, or the equivalent, is connected in the armature magne-tizing,` circuit, that is, between vthe brushes 1 and 3. as diagrammatically illustrated in Fig. 523. in this way, the inagnetizing` ellect ot the LLarmature turns proper is desirably assisted, as shown by the ihn; chart of i pi. 22, comparison being` had with 20. l y T he structure shown in the lower part of lll 22 comprises the armature with the pairs olf short-circuits1 brushes, as previously described. and stator S13., which is provided with the relatively large slots 30 and and a plurality ot smaller slots 3Q. as described in connection with Fig. 19, to- `rether with a plurality ot narrow slots 4:5, 45, and 4G', each having` a depth equal to that oit the large slots 30 and 31. These narrow slots are located-.opposite the several brushes ot the armature, slots and 4G being located in approximate alineinent with the brushes 1 and Q and beineY joined by an excitiiig-lield-windine; coil 48, while slots e5 and i6 are situated approyimatelyv opposite the lnushes 3 and Ll and are joined by the turns comprisingan exciting-fieldwindingr coil 19. The eXcitiiig-tield-winding coils 3T and 38 are again associated with the large slots 30 and 31. as previously described in connection with Figi. 19. inducing-lield-winding coils i3 and il are distributed through the smaller stator slots to produce the desired compensating` action.

lt will be observedV that the ellective torque-producing); or resultant i'lux in Fig. QQ is increased, under startingr conditions. over that obtained by the structure ot Fig. 19. the resultant .flux correspondingl to which structure is shown in Fig. 20.

The remaining` diagrammatic ligurcs illustrate various connections ot the lield and ai'- inaturc windings that may be employed in coniunctiou with the structure that is shown in Fis'. i2.

The sys-tem shown in Figi. Ql comprises a direct cmincction ot the eXcitin'-dclfl nzlcoil 3T and the inducing-'lield-i And'ng' coils il?) and di across the supply-circuit terminals l5 and 16. wliiletlie armature A. is connected. through the small-span. portion 18 ot the exciting field winding` in parallel relation, to a section oli the inducing-fieldwinding; coils. ln this way, the phase relations of. the armature magnetizing lcircuit may be adjusted yto satisfactorily cornpensate for ohmic resistance or to improve commutating conditions, as prev"ously exiplained.

The system shown in Fig. 25 discloses a different method for obtaining,lr the desired phase relation ot the armature magnetizing turns. In this system, the inducing-fieldwnding coils 43 and 44 are connected between the supply-circuit terminals 15 and 16, while the excitinglield-.vinding coil 37 is connected across the working-circuit brushes 1 and 2, and the exciting-tield-winding col 38 is similarly connected across the brushes 3 and 4. In addition, another exciting-fieldwinding;r coil 49, having a smaller span or polar tace, is connected across the brushes 3 and 2 and a second additional small coil 48 is connected across the same brushes. The combined action or". the various lield windings tends to produce the desired phase relations in the armature magnetizing circuit, under operating conditions, tor the following reasons. The small-span coils 43 and 49 produce a more pointed or peaked field-torni than the main exciting coils 47 and 48, and serve to assist the flux set up by the armature magnetizingj-circuit inductors, whereas the main coils oppose that flux, as previously explained.

Several other modifications ot' circuit connections, which are advantageous in various respects, are shown in the remaining iio'ures. The system illustrated in Fig. 26 comprises a direct connection ot the inducing-heldwindingf coils 43 and 44 and the exciting'- .field-winclini,r coil 37 across the suppiy-circuit terminals 15 and 16, while the excitinglieldovindingr coil 48 is connected across the brushes 1 and 3, and the excitingieldwimling coil 49 connected across the brushes 2 and 4. Furthermore, the mid-points et' the eliciting-lield-windinzgr coils 4S and 49 are connected to the respective terminals ot the inducing ield winding.

In Fig. 27. a similar arrangement of crcuits is provided in conjunction with a transformer that is interposed in the armature magnetizing circuit. The transformer is provided with a suitable core member 56 and a plurality ot coils 57, 58 aud 59 thatare respectively connected in series relation with the eXciting-tield-windin;r coils 49 and 48 and in parallel relation to the entire inducing field winding.

The system shown in Fig. 28 differs trom that illust-rated in Fig. 26 only in the connection of the mid-points of the exciting AField windings 48 and 49 directly across the supply-circuit terminals 15 and 16 instead of to the terminals of the inducing field winding.

In Fig. 29, the same Held-winding coils are employed and the entire inducingr tield windingr is again connected in series relaton with the eXciting-ield-winding coil 37 between the supply-circuit terminals. However, the exciting-tield-winding coil 4S is connected across the armature brushes 1 and 3, while the exciting-ield-winding coil 49 is connected across the brushes 2 and 4. The mid-points of the two windings just mentioned are respectively connected to the inner terminal of the inducing field-windingsT and to the supply-circuit terminal 16.

In Fig. 30, the secondary transformer winding T2 is shown as connected between the supply-circuit terminals 15 and 16, and thc entire inducing field winding is again connected in series relation with the exciting-lield-winding coil 37 across the transformer winding. The exciting-field-winding' coils 43 and 49 are again connected to the armature brushes, as described in connection with Fig. 29, the mid-point of the coil 48, however. beingT directly connected to an intermediate point of the transformer winding T2. while the mid-point of the coil 49 is connected to a point intermediate the inducing-field-winding coils and the exciting-field-winding coil 37.

In Fig. 31, the inducing field winding.;r is connected across a certain outer section of the transformer winding T2, While the ex- -iting-lielclwincling coil 37 is connected in series relation with the primary transformer winding T1 between the supply-circuit couductors Trolley and Ground. The remaining; e\'citirig-ficld-winding` coils 48 and 49 are again connected across the pairs of armature brushes 1 and 3 and 2 and 4, respectively, while the mid-points ot the coils 48 and 49 are respectively connected to the inner terminal of the inducing field Windinrj. that is. to an intermediate point in the secondary transformer winding T2 and to thc transformer terminal 16.

I do not wish to be restricted to the specific structural details, circuit connections, lor arranael'uent of parts herein set- `torth, as various further modifications may be eflcctcd without departing from the spirit and scope of my invention. I desire, theretore. that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

l. A dvramo-clectric machine comprising a comouitatfutype armature. a plurality of space/l sets of short-circuited brushes co-opcr :itincf theieexitli. a maginetizable stator membcr enclosingr said armature. an inrluciimr field winding distributed around said stator membcr. and an exciting1r field winding so located with respect to said brushes that thc magnetic leakage between said exciting field windingr and the armature turns connected by said sets of brushes is relatively large. the arrangement being` such vthat a resultant starting fiuX is produced.

2. A single-phase motor comprisingY ay Cil coinrnutator-type armature. a plurality ot brushes associated therewith to perniit niagnetizing currents to lflow in certain armature inductors, a inaggnetizable stator ineinber enclosing said armature, and an exciting' lield winding' producing' a ruagneto-inotire torce substantially coaxial with that ot' tile inagnetizing' armature inductors and haring its coil-sides so located with respect to said brushes 'that the magnetic leakage between said exciting' ield winding` and the arma* ture turns carrying' said inagnetizincr currentsis relatively large. the arrangement being such that a resultant starting` tlux is produced.

3. A singlephase motor comprising corninutator-type armatura a plurality ot brushes associated therewith to establish cert-ain Zones ot inagnetif/iingg-circuit inductors and ot working-circuit inductors in said armature7 a inagnetizable stator nieinber enclosingsaid armztture, and an excitingi'ield winding' producing a magneto-motive torce substantially7 coaxial with that ot the inagnetizing armature inductors and including' polar arc larger than the arc coyered by said armature working-circuit inductorsnl the arrangement being such that resultant starting' flux is produced.

4L. A single-phase inotor comprising' a conunutator-type armature. a plu 'ality ot brushes associated therewith to establish certain Zones ot inagrnetizi fg-circuit and otl working-circuit inductors in said armature, and a concentratefl-type exciting); stator held winding'.v producing' a magyjnetoanotiye 'torce substantially coaxial with that ot the inap;- netizingj armature inductors, the arrangienient beine' such that a resultant starting' flux is produced.

5. single-phase niotor comprising; a couunutator-type armature? a plurality ot brushes associated therewith to establish cortain alternate Zones oli inaginetizingcircuit and ot' working-circuit inductors, one set ot said :iones covering an arcuate distance ot approximately two-thirds the distance coyered by the othen and a stator-exciting; winding; circuniterentially distributed in a dilterent nie-.nner than the arinature-mag netiZing-circuit inductora tie arrraigreincnt being' such that a resultant starting' flux is produced.

6, single-iiliase uiotoi' comprising: a coniniutator-type armature.' a plurality.' ot spaced sets ot close-circuited lin'ushes fo-operating' therewith` the arcuate distance he tween pairs ol1 close-circuited lu'ushes and corresponding' to the number ot armature inductors included in the inagneti/.ing cl cuit heine` approximately equal to Gf/Ji ot the entire armature circurnterence., and a stator-exciting' winding` coyerinej a ina rially smaller percen gre et the circuiti ence. the arrangement being such that a resultant starting' tlu: is produced.

7. It single-phase niotor comprisinf;- connnutator-type arinature7 and a plurality ot spaced sets ot close-circuited brushes cooperating' therewith7 a inaegnetizable stator inen'iber enclosing' said armature, and an eX- citinp; held winding` producing a magnetoniotiye torce substantially coaxial with that oi' the inagnetizing' armature inductors and concentrated in stator slots separated by an arcuate distance materially different troni the arc included between adjacent unconnected brushes, the arrangement being such that a resultant starting' linx is produc/eav S. A. single-phase inotor comprisingV a coininutator-type in 'naature` a pliu'ality ot brushes associated therewith to establish eertain zones ot inagnetizincircuit and ot working-circuit inductors .in said arinature1 and an exciting` field windingincluding a polar arc materially ditl'erent troni the arc including said arniature working-circuit ine ductors, said field winding;- beine` synunetrically located opp site the Zones ot such inductors, the arrangement being; such that a resultant starting tlux is produced.

9. A single-phase motor comprising a coninnitator-type armature. a. plurality ot brushes associated therewith to establish certain Zones ot inagnetiZing-cireuit and ot working-circuit inductors in said armature. and an exciting' field-winding* concentrated in slots located opposite the central portions ot said Zones ot inagrnetiaing-circuit indue-- tors, the arrangement being' such that a rcsultant starting` tluX is produced.

10. A. single-phase .inotor comprising' a commutator-type armature.. a plurality ot spaced sets ot close-circuited brushes co-operating therewith, a inagnetir'iablc stator member enclosingr said armature, and an eX- citing;- lield windingl concentrated in stator slots respectively located midway between the brushes ot each close-oircuited set the arrangement being' such that a resultant starting' `flux is produced.

l1. A dynan'io-electrifl machine comprising'aeomniutator-type armaturen plurality ot spaced sets ot close-circuited brushes cooperating` therewith` a inaguetiaablo stator ineniber enclosing' said arniati-.ur` au iu ducinp; held winding` distriliuted around said stator rneinber. and an exciting; field winding so located on the stator with respect to said brushes that the magnetic leakage between said exciting` 'field winding and the arinature-exciting-inductors is relatiyely la rue. the arrangement beine' auch that a resultant starting' flux is produced.

12. A single-phase inotor comprising a commutator-type armature, a plurality ot brushes associated therewith to establish certain alternate zones ot niagnetiZing-eircuit and of working-circuit inductors, and a stator exciting winding producing a magneto- Inotive force substantially coaxial with that of the magnetizing armature inductors and circumierentially distributed in a different .manner than the armature magnetizing-cirenit inductorsl. the arrangement being such that a resultant starting flux is produced.

13. A single-phase motor comprising a comn'intatorype armature, a pluralityi of brushes associated therewith to permit magnetizing currents te flow in the' armature indnctors to set up a main field. a magnetizable stator member enclosing said armature, and exciting lielcl-ceiiductors on said stator member for setting up a field of substantially the same axis as that of said main field and being so located with respect to said brushes that the magnetic leakage between said stator-exciting-field-condnctors and the armature turns carrying said armature magnetizing currents is relatively large, the arrangement being` such that a resultant starting flux is produced.

14. A single-phase motor comprising a eommntator-type armature, a plurality l brushes associated therewith to establish certain Zones et magnetizing-circuit inductors and oif working-circuit indnctors in said armature, each magnetizing-circuit Zone being materially less than 180 electrical degrecsj a magnetizable stator member enclosing said armature, and an exciting field winding producing a magneto-motive force substantially coaxial with that of the magnetizing armature inductors and including a polar are larger than the arc covered by said armature working-circuit inductors, the arrangement being such that a resultant starting flux is produced.

15. f\ single-phase motor comprising a cominntator-type armature. a plurality of spaced sets ci" close-circnited brushes cooperating therewith, the arcuate distance between eacl pair of close-circuited brushes and corresponding to the number of armatiire inductors included in the magnetizing circuit being materially less than 180 electrical degrees, and a stator-exciting winding covering a materially smaller arcuate distance. 'the ngemcnt heilig such that a resultant .fz ng linx is produced.

1 6. it single-phase motor comprising a comnintator-type armature, and a plurality of spaced sets of close-cireuited brushes c0- operating therewith to establish certain zones of magnetiZing-circuit and of working-circuit inductors in said armature, each magnetiZing-circuit Zone being materially less than 180 electrical degrees7 a magnetizable stator member enclosing said armature, and an exciting field winding concentrated in stator slots separated by an arcuate distance materially different from the are included between adjacent unconnected brushes. 'the arrangement being such that a resultant starting flux is produced.

17.11 single-phase motor comprising a commutator-type armature. a plurality of brushes associated therewith to establish certain zones of niagnetizing-eircuit and of working-circuit inductors in said armature, each inagnetizing-circnit zone being materially less than 180 electrical degrees, and an exciting field winding concentrated in slots located opposite the central portions of said magnetizing-circuit zones, the arrangement being such that a resultant starting flux is produced.

18. A single-phase motor comprising a commutator-type armature, a plurality of brushes associated therewith to establish certain zones of magnetizing-circuit and of working-circuit indurtors in said armature, a magnetizable stator member enclosing said armature, and an exciting field winding on the stator so located with respect to said brushes that the resultant field acting upon the armature working-cnrrents is of a direction opposite to the field set up by said exciting field winding.

19. A single-phase motor comprising a commntator-type armature. a plurality of brushes associated therewith to establish certain zones of magnetizing-eircuit and of working-circuit inductors in said armature, and an exciting field winding concentrated in slots located opposite the central portions of said magnetiZing-circnit zones7 the arrangement of parts being such that the resultant field finx induces a voltage in said exciting field winding that is opposite to the actual finx produced by that winding. the resultant field flux being of such nature as to effect a predetermined degree of power- 'factor compensation.

20. A single-plaise motor comprising a commutator-type armature. a plurality of spaced sets of close-circnited brushes co-operating therewith, a magnetizable stator member enclosing said armature, and an exciting field winding concentrated. in stator slots separated by an arcuate distance materially different from the are included between adjacent unconnected brnshes, the arrangement of' parts being such that the resultant field acting upon the armature working-currents is of a direction opposite to the field set up by said exciting field winding. the resultant field fiux being 'inherently of such nature as to effect a ln'edetermined degree of power-factor compensation.

Q1. A single-phase motor comprising a. commutator-type armature7 a plurality of spaced sets of' close-circuited brushes co-operating therewith, an inducing field winding and an exciting field winding connected in series relation. and means for connecting' a portion of said inducing iield Winding in circuit With the pairs of close-circuited brushes.

22. A single-phase motor comprising a commutator-type armature, a plurality of spaced sets of close-circuited brushes co-operating therewith to establish certain Zones of magnetizing-circuit and of Working-circuit inductors in said armature, an inducing held Winding and an exciting lield Winding each having one terminal connected to one pair of close-circuited brushes, and means for connecting a portion ot said inducing lield Winding in circuit with the magnetizing-circuit inductors of said armature.

23. A single-phase` motor comprising a commutator-type armature, a plurality of spaced sets of close-circuited brushes co-operating therewith, an inducing field Winding and an exciting eld Winding connected in series relation, and means :tor interconnecting said inducingr ield Winding With the pairs of close-circuited brushes, the arrangement being such that the current-flow in said Winding is affected by the current-flow in said brushes.

24h A single-phase motor comprising a commutator-type armature, a plurality oi; spaced sets of close-circuited brushes (3o-op erating` therewith to establish certain zones of magnetiZing-circuit and of Working-circuit inductors in said armature, an inducing field Winding and an exciting ield Winding each having one terminal connected to one pair ot -close-circuited brushes, and means for interconnecting said inducing field Winding with the pairs of close-circuited brushes, the arrangement being such that the circuit-flow in said Winding is affected' by the currentii0w in said brushes.

In testimony whereof, I have hereunto subscribed my name` this 29th day ol Oct.,

RUDOLF E. HELLMUND. 

